Work around downrev gccs which do not inherit visibility of the
Registry<>::iterator member class.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@43122 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/TargetMachineRegistry.cpp b/lib/Target/TargetMachineRegistry.cpp
index 077b7e8..3b43eb8 100644
--- a/lib/Target/TargetMachineRegistry.cpp
+++ b/lib/Target/TargetMachineRegistry.cpp
@@ -32,7 +32,7 @@
 TargetMachineRegistry::getClosestStaticTargetForModule(const Module &M,
                                                        std::string &Error) {
   std::vector<std::pair<unsigned, const entry *> > UsableTargets;
-  for (iterator I = begin(), E = end(); I != E; ++I)
+  for (Registry<TargetMachine>::iterator I = begin(), E = end(); I != E; ++I)
     if (unsigned Qual = I->ModuleMatchQualityFn(M))
       UsableTargets.push_back(std::make_pair(Qual, &*I));
 
@@ -60,7 +60,7 @@
 const TargetMachineRegistry::entry *
 TargetMachineRegistry::getClosestTargetForJIT(std::string &Error) {
   std::vector<std::pair<unsigned, const entry *> > UsableTargets;
-  for (iterator I = begin(), E = end(); I != E; ++I)
+  for (Registry<TargetMachine>::iterator I = begin(), E = end(); I != E; ++I)
     if (unsigned Qual = I->JITMatchQualityFn())
       UsableTargets.push_back(std::make_pair(Qual, &*I));